When someone (most likely a family member) posts on Facebook, news that announces first another person's news.
(v.) I can't believe my sister-in-law just Facethiefed us. I guess she thought it was her right to tell everyone we are expecting...
(n.) Well of course she wanted to let everyone know about our cousin's new "job, house, pet, promotion, love life, lottery winnings, etc.". She's a FaceThief.